As shown in FIG. 15, loading and unloading of containers Ct between container yards Yd and container ships Sh have conventionally been performed.
For example, in the case where a container Ct in a container yard Yd is loaded onto a container ship Sh, the container Ct is transferred from the container yard Yd onto a container conveying vehicle V such as a trailer by means of a transfer crane Tc or the like and then transported to an apron Ap. On the apron Ap, the container Ct is lifted by a spreader Sp of a container crane Cr and placed on top of another container Ct on a deck of the container ship Sb.
On the other hand, in the case of unloading a container Ct from the deck of the container ship Sh, the container Ct is lifted by the container crane Cr via the spreader Sp and moved to the apron Ap. Thereafter, the container Ct is transferred from the container crane Cr to the container conveying vehicle V and then transported from the apron Ap to the container yard Yd.
When containers Ct are stacked in multiple levels in the container yard Yd, on the container ship Sh, or in other places, in order to prevent the containers Ct from coming unfastened and shifted, for example, Patent Document 1 discloses a method in which a container coupling device is disposed between corner fittings provided on the bottom four corners of an upper container Ct and corner fittings provided on the top four corners of a lower container Ct to couple the containers Ct to each other.
A container coupling device of this type will be described with reference to FIGS. 16 to 20.
A container coupling device 100 includes a device main body 101 that is dividable into parts, which are fastened together into a single unit with a bolt. As shown in FIG. 19, the container coupling device 100 includes a shaft 102 that is axially supported in the device main body 101 in a rotatable manner. An upper cone 103 and a lower cone 104 shown in FIG. 16 are integrally connected to an upper end and a lower end of the shaft 102.
The device main body 101 includes an upper fitted portion 101U and a lower fitted portion 101D integrally formed, respectively, in an upper part and a lower part thereof and each having a shape that matches an engaging hole Fa (see FIG. 20(b)) of a corner fitting F of a container Ct. The upper fitted portion 101U and the lower fitted portion 101D can be fitted into the engaging hole Fa of a bottom corner fitting F of an upper container Ct and the engaging hole Fa of a top corner fitting F of a lower container Ct, respectively. The device main body 101 has a through hole (not shown) extending through the upper fitted portion 101U and the lower fitted portion 101D, and this through hole supports the shaft 102 in a rotatable manner.
It should be noted that the corner fittings F of the containers Ct are not shown in detail in the drawings, but are specified in JIS Z 1616 together with the engaging hole Fa.
The upper cone 103 and the lower cone 104 are engageable with the corner fittings F of the containers Ct through the engaging holes Fa and are individually formed in a shape corresponding to the engaging hole Fa of the corner fitting F as viewed from above. As the shaft 102 rotates, the upper cone 103 and the lower cone 104 rotate on a top surface of the upper fitted portion 101U and a bottom surface of the lower fitted portion 101D, respectively, of the device main body 101.
The upper cone 103 and the lower cone 104 are integrally connected to the shaft 102 so as to cross in an X shape as viewed from above so that when the upper cone 103 is inserted into or released from the engaging hole Fa of the bottom corner fitting F of the upper container Ct, the lower cone 104 is engaged with the top corner fitting F of the lower container Ct, and when the lower cone 104 is inserted into or released from the engaging hole Fa of the top corner fitting F of the lower container Ct, the upper cone 103 is engaged with the bottom corner fitting F of the upper container Ct.
Here, the lower cone 104 is formed in such a shape that when the lower cone 104 is in a position at which the lower cone 104 crosses the engaging hole Fa of the corner fitting F, a rotational force is applied to the lower cone 104 when the lower cone 104 is forced against the engaging hole Fa of the corner fitting F. That is to say, the lower cone 104 is formed in such a manner that in a state in which the lower cone 104 crosses the engaging hole Fa of the corner fitting F with the shaft 102 in a first rotation position A (described later), when the lower cone 104 is forced against an outer circumferential edge of the engaging hole Fa of the corner fitting F, a pressing force is exerted on the corner fitting F via the lower cone 104, while the lower cone 104 receives a reaction force, and the reaction force acting on the lower cone 104 causes the lower cone 104 to rotate around a rotation axis of the shaft 102.
As shown in FIG. 19, a cavity 101X having a first locking portion 101a and a second locking portion 101b is formed inside the device main body 101. An arm 1021 integrally fixed to the shaft 102 can abut against the first locking portion 101a and the second locking portion 101b. The shaft 102 can rotate between the first rotation position A at which the arm 1021 abuts against the first locking portion 101a of the cavity 101X and a third rotation position C at which the arm 1021 abuts against the second locking portion 101b. 
A torsion spring 105 is disposed on the shaft 102. The torsion spring 105 biases the shaft 102 so that the arm 1021 abuts against the first locking portion 101a of the cavity 101X. A groove 1022 is formed in a circumference of the shaft 102. A wire 106 is wound on the shaft 102 along this groove 1022. A loop portion at one end of the wire 106 is inserted through the arm 1021. The other end of the wire 106 is led outside through a mouthpiece 107 slidably disposed on the device main body 101, and is anchored to an operation knob 108.
A locking member 1061 is formed in the vicinity of the other end of the wire 106. Right and left ends of this locking member 1061 can be selectively locked in slots 107a and 107c formed in an upper part and a lower part of the mouthpiece 107 that is slidably fitted in a guide 101Y of the device main body 101.
The mouthpiece 107 is disposed with its right and left ends both being fitted in the guide 101Y of the device main body 101, so as to be slidable along the guide 101Y. Moreover, the mouthpiece 107 is biased by a spring 109 disposed on the device main body 101 so as to abut against an end of the guide 101Y.
As shown in FIG. 15, in coupling together vertically adjacent containers Ct on the container ship Sh, first, a container Ct is transferred from the container yard Yd onto the container conveying vehicle V by using the transfer crane Tc or the like and transported to the apron Ap. Then, on the apron Ap, the container Ct is lifted to and stopped at a level of about one meter above the ground by the spreader Sp of the container crane Cr. Here, as shown in FIG. 20(a), the upper cone 103 of the container coupling device 100 is attached to the bottom corner fitting F of the container Ct.
Specifically, an operator grasps and pulls the operation knob 108 to lock the locking member 1061 of the wire 106 in the slot 107a of the mouthpiece 107. In this state, the shaft 102 is in the third rotation position C at which the arm 1021 abuts against the second locking portion 101b of the cavity 101X of the device main body 101. Moreover, the upper cone 103 is in a position at which the upper cone 103 overlaps the upper fitted portion 101U of the device main body 101 as viewed from above. Thus, the operator can insert the upper cone 103, together with the upper fitted portion 101U of the device main body 101, into the engaging hole Fa of the bottom corner fitting F of the upper container Ct.
Once the operator has inserted the upper cone 103 into the corner fitting F through the engaging hole Fa, the operator again grasps and pulls the operation knob 108 to release the locking member 1061 of the wire 106 from the slot 107a of the mouthpiece 107. As a result, the shaft 102, due to a biasing force of the torsion spring 105, returns to the first rotation position A at which the arm 1021 abuts against the first locking portion 101a of the cavity 101X of the device main body 101. In this state, as described above, the upper cone 103 and the lower cone 104 of the container coupling device 100 are positioned such that the cones individually cross the engaging hole Fa of the corner fitting F. Thus, the upper cone 103 is engaged with the corner fitting F, and the container coupling device 100 is retained by the bottom corner fitting F of the container Ct without falling out.
As shown in FIG. 20(b), when the container coupling device 100 has been attached to the bottom corner fitting F of the container Ct, next, the container Ct can be lifted by the container crane Cr and placed on top of another container Ct on a deck of the container ship Sh. At this time, the lower cone 104 of the container coupling device 100 is forcibly rotated against the biasing force of the torsion spring 105 along the outer circumferential edge of the engaging hole Fa of the top corner fitting F of the other container Ct. Then, when the lower cone 104 overlaps the lower fitted portion 101D of the device main body 101 as viewed from above, the lower cone 104, together with the lower fitted portion 101D of the device main body 101, is fitted into the engaging hole Fa of the top corner fitting F of the other container Ct. Once the lower cone 104 has been fitted into the top corner fitting F, the lower cone 104, due to the biasing force of the torsion spring 105, returns again to the position at which the lower cone 104 crosses the engaging hole Fa of the corner fitting F, and thus engages with the corner fitting F. Consequently, as shown in FIG. 20(c), the upper and lower containers Ct are coupled together by the upper cone 103 of the container coupling device 100 engaged with the bottom corner fitting F of the upper container Ct and the lower cone 104 of the container coupling device 100 engaged with the top corner fitting F of the lower container Ct.
On the other hand, as shown in FIG. 20(d), in the case of unloading containers Ct from the deck of the container ship Sh, the operator pulls or pushes the operation knob 108 downward from on the deck to lock the locking member 1061 of the wire 106 in the slot 107c of the mouthpiece 107. In this state, the shaft 102 is in a second rotation position B at which its arm 1021 is located between the first locking portion 101a and the second locking portion 101b of the cavity 101X of the device main body 101. The lower cone 104 is overlapping the lower fitted portion 101D of the device main body 101 as viewed from above. As a result, the lower cone 104 of the container coupling device 100 can be released through the engaging hole Fa of the top corner fitting F of the lower container Ct.
Then, after the container Ct is lifted and moved via the spreader Sp of the container crane Cr and stopped at a level of about one meter above the ground of the apron. Ap, the upper cone 103 of the container coupling device 100 is released from the bottom corner fitting F of the container Ct. The operator grasps and pulls the operation knob 108 to lock the locking member 1061 of the wire 106 in the slot 107a of the mouthpiece 107. In this state, as described above, the shaft 102 is in the third rotation position C at which its arm 1021 abuts against the second locking portion 101b of the cavity 101X of the device main body 101. Moreover, the upper cone 103 is overlapping the upper fitted portion 101U of the device main body 101 as viewed from above. Thus, as shown in FIG. 20(e), the upper cone 103 of the container coupling device 100 can be released from the engaging hole Fa of the bottom corner fitting F of the container Ct. Afterward, the container Ct is transferred from the container crane Cr onto the container conveying vehicle V and transported from the apron Ap to the container yard Yd.
As described above, with the container coupling device 100, during loading of containers Ct, the container coupling device 100 is attached to a bottom corner fitting F of a container Ct to be loaded, and the container Ct is then placed on top of another container Ct. When the lower cone 104 has been rotated along the outer circumferential edge of the engaging hole Fa of a top corner fitting F of the lower container Ct and fitted into the corner fitting F, the lower cone 104 is automatically returned to the position at which the lower cone 104 engages with the corner fitting F by the torsion spring 105. As a result, the upper and lower containers Ct can be coupled together.
Moreover, during unloading of containers Ct, it is necessary to operate the operation knob 108 to rotate the lower cone 104 against the biasing force of the torsion spring 105 from the position at which the lower cone 104 engages with the corner fitting F to the position at which the lower cone 104 can be inserted or released. That is to say, as shown in FIG. 20(d), the operator is required to pull or push the operation knob 108 downward from on top of the uppermost container Ct of containers Ct stacked in multiple levels or from the deck (in the case of the container ship Sh) or the ground (in the case of the container yard Yd) by using a long tool to lock the locking member 1061 of the wire 106 in the slot 107c of the mouthpiece 107.
In this case, it is difficult for the operator to reliably operate the operation knob 108 with the tip of the long tool, and therefore, there are problems in that much time is needed for the work and that operating the heavy, long tool causes intense fatigue. Moreover, when the operator performs the operation from on top of the uppermost container Ct, the operator works at a high place, which entails danger such as accidentally falling down, and so there also is a drawback in terms of safety.
In view of these problems, for example, Patent Documents 2 and 3 propose a container coupling device referred to as a fully automatic container coupling device. With the fully automatic container coupling device, even during unloading of containers Ct, a container Ct to be unloaded is lifted via the container crane Cr. Thus, the lower cone is rotated against the biasing force of the torsion spring along the edge of the engaging hole Fa of the top corner fitting F of a lower container Ct to reach the position at which the lower cone overlaps the lower fitted portion of the device main body, whereas the upper cone is engaged with the bottom corner fitting F of the upper container Ct, and in this state, the lower cone is released from the engaging hole Fa of the top corner fitting F of the lower container Ct.    Patent Document 1: WO 92/05093A1    Patent Document 2: JP 2006-76636A    Patent Document 3: JP 2007-1661A